1. Field of the Invention
The present invention relates to a displaying function for a portable device such as a pager, a handy game device, a watch, and so on.
2. Description of the Related Art
Referring to FIG. 1, FIG. 2A and FIG. 2B, the prior art is described. As illustrated in FIG. 1, a liquid crystal cell 22 comprises a display section 27a for blocking a light beam and indicating figures and graduations upon being driven electrically, a non-display section 27b for transmitting a light beam upon being driven electrically, and a background section 27c for always transmitting a light beam without being driven electrically. A masking plate 21 is formed of an optical motionless display pattern 31 such as a punched pattern in which a character, a fixed graduation, a frame and a design are colored appropriately. The other portion of masking plate 21 is a transparent window section 32. A light beam source 23 is a surface-shaped light emitting source.
Referring to FIG. 2A, in the display section, the effect of a light beam emitted from the outside is explained. When a light beam 24b passed through the window section 32 of the masking plate 21 reaches the display section 27a of the liquid crystal cell 22, the display section 27a blocks and absorbs the light to thereby be perceived as a dark portion when viewed from the outside (the left side in the figure).
When a light beam 25b passed through the window section 32 of the masking plate 21 reaches the non-display section 27b or the background section 27c of the liquid crystal cell 22, it can be transmitted through the liquid crystal cell 22 with very little loss of light so as to arrive at the surface light source 23 whereupon it is reflected and transmitted again through the liquid cell 22 and the masking plate 21 to reappear on the outside as a light beam 25c. Therefore, the light beam 25c reappearing outside is perceived as a surface color of the surface light source 23.
A light beam 26b which has reached the motionless display pattern 31 of the masking plate 21 cannot pass through the masking plate 21, but instead is reflected by the motionless display pattern 31. The reflected light beam 26c is then perceived as a color of the motionless display pattern 31.
Referring to FIG. 2B, in the display section, the effects of a light beam emitted from the inside is explained. When a light beam 28 generated from the light source 23 reaches the display section 27a of the liquid crystal cell 22, the display section 27a blocks and absorbs it to thereby be perceived as a black or dark portion when viewed from the outside (the left side in the figure).
When a light beam 29 produced by the light source 23 reaches the non-display section 27b or the background section 27c of the liquid crystal cell 22, it can be transmitted through the liquid crystal cell 22 with very little loss of light so as to pass through the window section 32 of the masking plate 21 and resultingly be emitted towards the outside. Accordingly, the emitted light beam 29 is perceived as the luminescent color of the light source 23.
When a light beam 30 generated from the light source 23 and passed through the background section 27c of the liquid crystal 22 reaches the motionless display pattern 31 of the masking plate 21, the light beam is blocked, absorbed or reflected by the motionless display pattern 31 so that it cannot be allowed to be emitted to the outside. Accordingly, this portion is perceived as a black or dark portion when seen from the outside.
As mentioned above, when the display section is viewed upon being lit with outside light, a brightness display is perceived where the color of the light source 23 is light and the light blocking portion caused by the display section 27a is dark, and a color display is perceived at the motionless display pattern 31.
On the other hand, when the display section is perceived using an inside light, a brightness display is recognized where the luminescence light caused by the surface light source 23 is light and the light blocking portion caused by the display section 27a and the fixed display section is dark.
The first problem with such a conventional visual display unit is that a colored punched pattern drawn on the motionless display section of the masking plate is rendered meaningless because only the brightness display is viewed as the display section.
The cause of this problem is that the punched pattern blocks light from passing therethrough and so cannot send frontward any color information of the light emitted from behind the pattern.
The second problem is such that the punched pattern on the masking plate is subjected to restrictions on the degree of freedom in its pattern layout because it must be designed in such a manner as to avoid covering the display of the liquid crystal cell.
This is because the punched pattern is adapted to block light and so shields the display of the liquid crystal cell if the latter is positioned behind the former.
Even if the masking plate is interposed between the liquid crystal cell and the light source, while the display of the liquid crystal cell can be seen where it is superposed on the masking plate, the punched pattern blocks the light emitted from the light source and eventually prevents the display of the liquid crystal cell from being brightly illuminated.
The third problem is that the punched pattern does not necessarily constitute an appropriate pattern for a particular display on the liquid crystal cell which is intended to be provided with a variety of visual contents.
The reason for this problem is that since the pattern of the masking plate intended to decorate the display of the liquid crystal cell is a motionless display pattern, it must rely on the display contents of the liquid crystal cell to be relatively unvarying or otherwise employ a plain and acceptable pattern of the masking plate that would not clash or interfere with the display contents of the liquid cell.